1. Field of the Invention
The invention relates to a method for incorporating animal protein into a biscuit dough to obtain a dry, hard canine biscuit. The invention also relates to a dry, hard canine biscuit.
2. Description of the Prior Art
Dry pet foods are commonly cereal type materials having a low moisture content of less than about 15 percent by weight. As a result of their low moisture content, they resist mold growth and bacterial spoilage. Additionally, they can often be packaged and stored in containers, such as a box, without the need for hermetic sealing and without the need for a moisture barrier. Dry pet foods typically have low palatability because of their low moisture content.
The incorporation of meat products, fish products and poultry products into a farinaceous pet food to improve palatability and to improve nutritional values of dry pet foods, intermediate moisture products and high moisture content pet foods (more than about 50 percent by weight water) is known in the art.
U.S. Pat. No. 3,946,123 discloses an aqueous suspension or broth of meat and meat by-products consisting in part or entirely of fish and flavored cereal chunks. The meat and meat by-products that may be used include those of fowl and fish as well as that of mammal such as cattle, swine, goats and the like. Due to the high moisture content of the product, it must be packaged in cans. In U.S. Pat. No. 4,158,706 a high moisture pet food product containing farinaceous and proteinaceous components such as meats, fish and poultry is impregnated with a preservative such as succinic acid to enable packaging within a paper or polymer film. These high moisture content products have a high shipping weight for a given amount of nutritive value and do not provide a hard surface for the strengthening of gums and for the removal of plaque from teeth.
The production dry pet foods which contain proteinaceous and farinaceous material is disclosed in U.S. Pat. Nos. 3,962,462, 4,020,187, 4,039,689, 4,055,681, 4,145,447, 4,215,149 and 4,229,485.
In U.S. Pat. No. 3,962,462 the ingredients are first dry-blended and then water and water-containing ingredients are added until a cohesive dough is formed. A stabilizing system comprising a sugar, an edible acid and an antimycotic provides stability within the pet food when the pet food is subjected to semi-moist conditions. The product is produced in wafer form for packaging with a semi-moist pet food. The proteinaceous material includes meat, such as the flesh of cattle, swine, sheep, poultry and fish as well as various meals such as meat and bone meal, fish meal and the like.
In U.S. Pat. No. 4,020,187 tallow or lard is added to a water slurry of a ground mixture of meat and meat by-products to raise the resulting fat content of the mixture to at least 25 percent. The resultant mixture is then homogenized to liquefy and reduce the particle size to uniformly distribute the fat content through the meat mixture. Dry farinaceous ingredients are ground and added to the homogenized meat mixture. The blended mixture is subjected to a temperature of from 225.degree. to 325.degree. F. at a pressure of at least about 50 p.s.i. The product is expanded, cut and dried to obtain a product having a final moisture content of from 7 to 15 percent. The product, it is disclosed, is not externally greasy and may be packaged in ordinary paper bags or in plastic wrap.
A dry, but soft, pet food is produced in U.S. Pat. No. 4,039,689 using low temperatures and pressures. The use of the low processing temperatures, less than about 130.degree. F., leads to the soft dry nature of the pet food, it is disclosed. Meat and meat by-products as well as dried animal by-products can be used as a protein source for the pet food in U.S. Pat. No. 4,039,689. The dried animal by-products include meat and bone meal.
U.S. Pat. No. 4,055,681, like U.S. Pat. No. 4,039,689, produces a soft dry pet food having a meat-like texture and appearance. Meat meal is disclosed as a protein source and fresh meat and meat by-products are used to impart palatability to the pet food.
In the production of the dry pet food products according to the processes of the above patents, the use of wet meat products cause substantial smearing or blending of the meat into the farinaceous material. It also causes bleeding of the protein colors into the farinaceous material which reduces the visual attractiveness of the product to the consumer and which reduces the product's hardness.
A hard dry pet food is produced in U.S. Pat. No. 4,145,447. High pressures of at least about 100 p.s.i. are used to obtain a product which is hard enough to provide chew-resistance for the removal of plaque or tartar from the animal's teeth. The product is a long-lasting one which requires about 30 minutes to 2 hours for a 25 lb. dog to consume. Dry components are mixed until homogeneous and then sufficient water is added to wet the product without affecting the apparent dry, free-flowing characteristic of the product. The wetted product is then compacted, at a pressure of at least 100 p.s.i., followed by heating or baking the compacted product at a temperature of at least 200.degree. F. The product can contain air-dried, freeze-dried or irradiated foods such as meat, fish, fish meal, cereals, fruits, vegetables and the like. Protein fibers, such as those derived from soy protein and wheat gluten, or animal fibers, such as those derive from skin, muscles, and intestines, are optionally added to support the structure of the product. The animal fibers can be prepared by cutting, chipping, grinding, shredding, shearing or beating animal skins such as cowhide or rawhide. The high pressures used in the process of U.S. Pat. No. 4,145,447 make the process costly. Also, the structure-supporting fibers derived from animal tissue, which are optionally used in the process of U.S. Pat. No. 4,145,447, are low in palatability. Furthermore, a product having discrete, visually apparent, meat particles is not disclosed.
U.S. Pat. Nos. 4,125,149 and 4,229,485 disclose processes for improving the palatability of dry pet foods by applying a coating which contains proteins derived from animals, to the surface of the pet food. In U.S. Pat. No. 4,215,149 the surface of the pet food is treated with fat and then with a phosphoric acid salt. Treatment of the surface of the pet food with meat flavors and animal proteins is optional. Heating of the coated pet food, it is disclosed, must be avoided.
In U.S. Pat. No. 4,229,485 a dry biscuit is coated with a continuous glazed liver coating and is then baked to less than 18 percent moisture by weight. The liver preferably constitutes at least about 50 percent by weight of the coating, exclusive of moisture. The liver coating contains farinaceous material and comminuted liver. The hard glazed coating, it is disclosed, has the visual appearance of a meat coating to enhance the product's attractiveness to pets. The dry biscuits to which the liver coating is applied are obtained by baking a combination of uncooked farinaceous material and uncooked meat or meat by-products. The use of the uncooked meat or meat-products in the form of finely cut flakes, preferably having their largest dimension in the range of 15/1000 inch to 250/1000 inch, it is disclosed, is necessary for obtaining high palatability of the product. However, the use of uncooked meat or meat by-products results in the blending of the protein color into the farinaceous material. Additionally, the flakes present in the biscuit are not visually apparent because of the liver coating.
U.S. Pat. No. 4,310,558 teaches producing a dry pet food product containing fibrous food pieces having a tough, pliable texture combined with a basal matrix containing proteinaceous and farinaceous materials having a porous texture and appearance. The fibrous food pieces, which may simulate vegetables, grains and red meat pieces, comprise denatured proteinaceous material. The food pieces are blended with undenatured proteinaceous materials and farinaceous materials. The mixture is mechanically worked under conditions of elevated temperature and pressure and finally extruded to form an expanded dry pet food product having a porous texture interspersed with food pieces having a tough, pliable fibrous texture. The mechanical working and forming is basically done in a cooker extruder, which utilizes high shear and substantial pressure.